B2.2 Size Flashcards
Surface area to volume ratio
Surface of an area per unit volume of an object
Format surface area to volume ratio should be presented in
Ratio
Surface area : volume
It should be simplified so volume = 1cm³
Why a tapeworm can rely upon diffusion alone to provide nutrients, where as multicellular organisms cannot
The larger the surface area to volume ratio the more easily and quickly nutrients can diffuse, as diffusion ratio is small e.g the tape worm
Increase size of organism = decrease surface area to volume ratio,
therefore diffusion distance becomes to great to allow an organism to meet the cells’ demands
Examples of adaptations to animal cells to improve surface area to volume ratio
Villi - intestines
Microvilli - Cilliated epithelial cells lungs
Alveoli - spherical shape
Adaptations to plants to increase surface area to volume ratio
Broad flat leaves - increase SA for capturing light & gaseous exchange via the stomata
Root hair cells
Adaptations of the lungs to maximise the rate at which oxygen enters the body
Single cell wall
Ventilation moves air in and out of lungs to maintain concentration gradient
Capillary network means good blood supply, which maintains concentration gradient
Spherical shape increases surface area
Adaptations of villi to maximise rate of diffusion and active transport in the small intestine
Single cell wall
Capillary network means good blood supply, which maintains concentration gradient
Fingerlike shape increases surface area
Microvilli increases surface area further
Many mitochondria to provide energy for active transport
Why transport systems are needed
To transport a substance to where it is needed once it has diffused
Transport systems in humans
Respiratory
Circulatory
Digestive
Endocrinology
Nervous
Urinary
What is the circulatory system
Heart and blood vessels
Circulatory system of a fish compared to human circulatory system
Fish have a single circulatory system, humans have a double circulatory system
State difference between oxygenated and deoxygenated blood
Oxygenated = high levels of oxygen
Deoxygenated = low levels of oxygen
Name the the three types of blood vessel shown below.
/ / /.:. ./ / /
◎ / ◎./ ◉/
[x2] [x2000] [x2]
A B C
A = vein
B = capillary
C = artery
Name adaptations of the three blood vessels
Vein: thin outer wall, thin layer of muscle and elestic fibres, large lumen
Capillary: very small lumen, single cell wall
Artery: thick outer wall, thick layer of muscle and elestic fibres, small lumen
Why humans have a double circulatory system
Consists of 2 circuits joined together
First circuit pumps deoxygenated blood to lungs to take in oxygen, and then returns oxygenated blood to heart
Second circuit pumps oxygenated blood all around the other organs of body and returns deoxygenated blood to heart
Benefits of having a double circulatory system
Deoxygenated and oxygenated blood does not mix
Blood is under higher pressure as it does not have to travel as far
High pressure means the materials are transported around the body faster
Difference between cardiac muscle and the muscles in the rest of your body
Heart is made of cardiac muscle that contracts without recieving nerve impulses from our brain
Muscle in the rest of your body (e.g in your arm) require a nervous signal to stimulate contraction
Parts of a heart
. Pulmonary vein
I———————->LUNGS—————————
Pulmonary I ┌──────-─┬───────┐ I
Artery I | | | I
I————+ >│Right atrium │Left Atrium │<—I
I I ├───v────┼────v──┤
I I—-| | |—
Vena cava │Right Ventricle │ Left Ventricle | I
I └──────-─┴───────┘ I
L________________________BODY<____________________I
Aorta
. Pulmonary vein
I———————->LUNGS—————————
Pulmonary I ┌──────-─┬───────┐ I
Artery I | | | I
I————+ >│Right atrium │Left Atrium │<—I
I I ├───v────┼────v──┤
I I—-| | |—
Vena cava │Right Ventricle │ Left Ventricle | I
I └──────-─┴───────┘ I
L________________________BODY<____________________I
Aorta
Right side is deoxygenated
Left side is oxygen rich
Pathway through the human circulatory system
Deoxygenated blood enters lungs
Oxygen enters blood - CO2 leaves
Blood enters heart through pulmonary vein, into the left atria
Blood is pumped through the heart from left artria to left ventricle, via bicuspid valve
Blood is pumped out of left ventricle through Aorta and goes to rest of the body
Oxygen diffuses out of the blood and CO2 diffuses in
Blood enters right atria of heart through vena cava
Blood is pumped through heart from right artria to right ventricle, via tricuspid valve
Blood is pumped out of right ventricle, to return to lungs via pulmonary artery
4 key components of blood and their function
Red blood cells - small biconcave cells containing haemoglobin and have no nucleus to enable and maximise oxygen transport
Small in size, which guarantees passage even through tiny capillaries
White blood cells - large cells fight disease by making antibodies, or changing their shape to engulf pathogens
Platelets - tiny structures/fragments of cells that help blood to clot
Plasma - Made up of 90% water, fluid in which the other components of blood float within
Acts as a transport medium for digested food, waste products, hormones and antibodies
Type of blood cell which is most common in the blood
Red blood cells
Xylem
Transports water and mineral ions from roots to stem, leaves and flowers
End walls of dead xylem cells broken to allow water and dissolved minerals to move through
Function of phloem
Transports dissolves sugars from photosynthesis, and other soluble food molecules from leaves to all other areas of the plant
Structure formed by xylem and phloem within the plant
Vascular bundle
What tissue makes up bulk of plant in woody plants like trees
Xylem
Experiment that can be done to easily visualise the xylem in plant tissue
Place celery in a jug of water containing food colouring
Leave for 24 hours
Cut slice of celery and veiw using magnifiying glass or light microscope
Structure of xylem
Made from dead cells
No cell walls at ends of cells
Dead cells form tubes for water and mineral ions to flow
Xylem cellulose cell wall is thickened and stiffened with lignin to provide support
Structure of phloem
Made of living cells
Cell walls connecting these cells do not completely breakdown creating sieve plates
Sieve plates allow dissolved sugars to pass
Connected cells form a tube allowing dissolved sugers to be transported
Direction of flow in xylem
One way - Roots to leaves
Direction of flow in the phloem
Two-way / bidirectional
Tissue in a plant which would transport glucose
Phloem
If a cross section was taken through the plant in the stem, where would you expect vascular bundle to be found
Bundles organised spherically in the cortex: cross section of the stem
Larger phloem at top of the bundle with smaller xylem tubes underneath
If a cross section was taken through the plant in the root, where would you expect the vascular bundle to be found
Bundle in the centre of the root
Xylem in the centre of the bundle
Phloem around the outside of the xylem
Surrounded by ground tissue
If a cross section was taken through the plant in the leaf, where would you expect the vascular bundle to be found
In spongy mesophyll layer
Xylem closest to palisade mesophyll layer (towards top of the leaf)
Phloem closest to the lower epidermis
How vascular bundles provide support
In the leaf they form a network that supports softer tissue
In the stem they are loacted around the outer edge providing the stem with strength to resit bending
In the root they are found in the centre to enable the root to act as an anchor
Transpiration
Movement of water through xylem
Explain the transpiration stream
The stream of water though the plants xylem caused by the loss of water through the plants stomata in the wind
Water evaporates through stomata
Water potential gradient between leaves and stem - water moves into leaves by osmosis
Water potential gradient between stem and roots - water moves into stem by osmosis
Water potential gradient between roots and soil - water moves into root hair cells by osmosis
What makes water vapour diffuse from the inside of a cell into the air
Water evaporates from inside leaf into leaf’s air spaces
Concentration gradient forms between the air inside leaf and the air outside the leaf
Water vapour diffuses from the area of high concentration or the air inside the leaf, to area of low concentration of air outside the leaf
Structure of stomata and how they open and close to control gaseous exchange
Stomata are made up of 2 guard cells
When there is plenty of light and water the guard cells take up water by osmosis and become turgid,
The inner wall of the guard cell is thickened so the cell curves as it becomes turgid creating a gap between the two guard cells,
This gap is known as the stomata,
If conditions for photosynthesis are poor then the guard cells lose water and become flacid,
When the cells are flacid the gap between them closes
Explain why the upper surface of many leaves is covered in a thick, waxy cuticle?
To prevent uncontrolled water loss
In hot environemnts this layer is very think and shiny
Calculate rate of transpiration
Calculate the rate of movement of an air bubble using a potometer
Rate of movement = distance (mm) ÷ time (s)
Only an estimate as small volume of the water taken up by the shoot is used in leaves and not transpired
Why does the plants need for CO2 increase the rate of transpiration in a plant.
Plants need glucose for respiration
Glucose is product of photosynthesis
Photosynthesis requires carbon dioxide and water
Plant must open stomata to enable the diffusion of carbon dioxide into the leaf
Open stomata allows water vapour to leave the leaf via diffusion
Lose of water from leaf increases rate of transpiration
State the factors affecting the rate of transpiration
Light intensity = increase light, increase transpiration
Temperature = increase temperature, increase transpiration
Air movement = increase air movement, increase transpiration
Humidity = increase humidty, decrease transpiration
What ringing experiment shows
A ring of bark is scraped away that also removes the phloem, exposing the xylem
Sugar then attempts to move down the stem but is stopped by the ring
This is demonstrated by a bulge of sugar forms above the ring
Suggesting that sugar moves down the stem in the phloem and sugar transported by the phloem
Explain how potometer experiment can be used to measure rate of transpiration
Set up potometer making sure the stem is cut under water to ensure no air bubbles
Release an air bubble into the capillary tube
As the water evaporates from the leaves and moves into the stem the bubble moves towards the plant
Measure how fast the air bubble travels
Refill and repeat the experiment
Difference in veins and arteries
Veins - blue - thin - carry blood to heart - valves along the length - wide lumen
Arteries - red - thick - carry blood away from heart - thick walls - narrow lumen diameter
Pulmonary artery
Heart pumps out deoxygenated blood to the lungs through this artery.
Pulmonary vein
Heart receives oxygenated blood from the lungs through this vein.
Coronary arteries have the same purpose:
The heart muscle is supplied with oxygenated blood through these arteries.
Vena cava
Heart receives deoxygenated blood from the body through this vein.
Aorta
Heart pumps out oxygenated blood to body through this artery
Pathway through human heart
Blood enters the heart via atria
Once filled with blood, atria contract, forcing blood down into ventricles below
When the ventricles contract, they force blood to exit heart
What happens when ventricles contract
they force blood to exit the heart
Why might someone be fitted with an artificial pacemaker
group of cells in right atrium act as a pacemaker to control heart’s beating -
If there are irregular heart rates, can be corrected using electrical devices known as artificial pacemakers
Difference between transpiration and translocation
Translocation is bidirectional (movement is both up and down the plant)
happens in the phloem NOT xylem
Unlike water transport (transpiration) which is unidirectional
Sample card
The heart muscle is supplied with oxygenated blood through these arteries.
